<?php  
  header("Content-type:text/html;charset=utf-8");  
  $linkurl = isset($_GET["linkurl"]) ? $_GET["linkurl"] : "";
  $fp = @fopen($linkurl,"r");
  if($fp==false){
	  echo "无效链接地址!";
  }else{
	  echo "有效链接地址!";
	  fclose($fp);
  }
?>